关于这张图
A long-lasting coronal hole has again rotated around to face the Earth (Nov. 28-30, 2018). This persistent hole - the elongated dark region seen in the still image - first appeared in July and has been observed each rotation of the Sun since. Coronal holes are the source of high-speed solar wind; when this one faced Earth, it sparked outbursts of aurora some of which were observed in our northern tier states. Coronal holes are magnetically open regions on the Sun that can last from days to months, although this one has lasted longer than most. The time-lapse video, taken in a wavelength of ext…
